Childhood obesity is recognized as a serious public health issue. At least 15 percent of children in the US aged 6-19 are overweight, and the percentage is increasing. Suboptimum diet and physical activity patterns appear to be contributing to this epidemic. The candidate is currently working on several research projects investigating the influence of environmental factors on food intake, weight status and physical activity behavior. It is not enough to address behavior changes alone;it is also necessary to address the environments in which these behaviors occur, including the environment at home, in school, and in the community. Children and adolescents spend a great deal of their time in school, and schools provide opportunities for eating and physical activity. It has been suggested that policy changes would be helpful in improving diet and physical activity in students. The applicant is interested in environmental influences on eating and physical activity and, in particular, on how policy changes can be used to modify the food and physical activity environments in schools to positively impact students'behavior. Studies proposed in the first two years of this project will take advantage of a school district that has already implemented innovative policy changes to modify the school food environment. The applicant proposes to evaluate existing policies in regards to other policy areas such as physical activity and nutrition education in the school district. The first 2 years will also be used to assess students'daily variability in physical activity using accelerometers. For the independent phase of the project (years 3-5), the applicant proposes to work with the school district in developing and implementing policies to positively impact the school physical activity and nutrition education environment using the pilot data accumulated during the first 2 years and to evaluate the impact of these policies on physical activity levels, nutrition knowledge and the behavior of students. The impact of these policy changes on the school food service revenues will also be investigated. This project will help demonstrate the impact of positive changes to the school environment on students'health related behaviors.